Like all other parts for custom PC building, you can either arbitrarily pick a pricepoint and a cool-sounding name and slap it together, or you can read benchmark comparisons and have a rough idea what works best for you. Should I buy an Intel CPU or AMD? Which of the dozen models from each brand? Motherboards, power supplies, cases, coolers, this staggering array of choice is everywhere throughout the custom PC space. You also have the option to not deal with it and buy a full PC from an OEM or system integrator, even Dell if you hate both yourself and your money.

PS the 3080 and the 3080 Ti are different GPUs, so that is nothing to do with the AIB manufacturers, that's Nvidia directly. Like an Apple M1 vs M1 Ultrapromax.